The present invention relates to a nozzle for simultaneous application of a string of glue on two facing, adjacent disc surfaces, especially for gluing together two optical disc elements of a digital video disc.
Our previously filed Swedish patent application SE-A-9601263-8 describes a process and a device for gluing together two optical disc elements, especially substrates for digital audio, video or computer discs, such as DVD:s (Digital Video Discs). The gluing together of the two disc elements is done by placing them coaxial to each other on individual holders in such a manner that a preferably radially outwardly widening gap is formed between the disc elements, whereafter a tubular glue injection nozzle is inserted into the gap to dispense a liquid adhesive so that it will essentially come into simultaneous contact with facing sides of the two disc elements, which are rotated at the same time one rotation to form a circular string of glue in contact with the two disc elements. When inserting the nozzle tube into the gap, they come very close to the disc elements. There will be only a few tenth of a millimeter play between the nozzle tube and the disc elements.
By increasing the rotational speed of the disc elements when applying glue and increasing at the same time the dispensing pressure of the adhesive, it is possible to increase the distance between the nozzle opening and the location on the disc elements where the glue string is to be applied and thus achieve a greater margin of safety against contact or hitting between the nozzle and the disc elements.
In order to assure that a major portion of the glue flow from the nozzle is directed towards and strikes the opposing disc element surfaces at the same time and that a smaller portion of the glue flow will flow straight ahead into the gap between the disc elements, it is suggested in accordance with the present invention that the nozzle have a channel outlet opening with upper and lower outlet areas and therebetween a constricted outlet area.
According to a preferred embodiment of the invention the nozzle has the shape of a tubular element with an axially forwardly directed, constricted end opening and two diametrically opposite, radially outwardly directed openings near the end of the tubular element.